Voltage regulator operable to switch between a two-stage structure operation and a three-stage structure operation
a voltage regulator and three-stage structure technology, applied in the direction of differential amplifiers, amplifiers with semiconductor devices/discharge tubes, instruments, etc., can solve the problems of increasing chip area, difficult to significantly improve the power supply voltage rejection ratio and the transient response characteristic, and the three-stage structure is not suitable to achieve low power consumption
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first embodiment
[0037]FIG. 1 is a circuit diagram illustrating a voltage regulator according to a first embodiment of the prevent invention.
[0038]The voltage regulator according to the first embodiment includes a reference voltage circuit 109, an output transistor 147, a voltage dividing circuit 127, differential amplifier circuits 124 and 125, bias circuits 122 and 123, and a control circuit 121.
[0039]Next, the connection of the constituent circuits of the voltage regulator according to the first embodiment is described.
[0040]An output terminal of the reference voltage circuit 109 is connected to a non-inverting input terminal 108 of the differential amplifier circuit 124 and an inverting input terminal 105 of the differential amplifier circuit 125. An output terminal of the differential amplifier circuit 124 is connected to an input terminal 104 of the differential amplifier circuit 125. An output terminal of the differential amplifier circuit 125 is connected to a gate of the output transistor 1...
second embodiment
[0057]FIG. 3 is a circuit diagram illustrating a voltage regulator according to a second embodiment of the present invention.
[0058]The voltage regulator according to the second embodiment includes the reference voltage circuit 109, the output transistor 147, the voltage dividing circuit 127, the differential amplifier circuits 124 and 125, a bias circuit 310, and the control circuit 121. FIG. 3 is different from FIG. 1 in that the bias circuit 310 is provided instead of the bias circuits 122 and 123.
[0059]Next, the connection of the constituent circuits of the voltage regulator according to the second embodiment is described.
[0060]The connection of the bias circuit 310 is described.
[0061]A gate and drain of a P-channel transistor 301 are connected to the constant current circuit 131 and a gate of a P-channel transistor 302, and a source thereof is connected to the power supply terminal 101. A drain of the P-channel transistor 302 is connected to the switching circuit 150 and a sourc...
third embodiment
[0068]FIG. 4 is a circuit diagram illustrating a voltage regulator according to a third embodiment of the present invention.
[0069]The voltage regulator according to the third embodiment includes the reference voltage circuit 109, the output transistor 147, the voltage dividing circuit 127, the differential amplifier circuits 124 and 125, the bias circuit 310, and an external terminal 401. FIG. 4 is different from FIG. 3 in that the control circuit 121 is removed and the external terminal 401 is provided. The external terminal 401 is connected to the switching circuit 150.
[0070]Next, an operation of the voltage regulator according to the third embodiment is described.
[0071]A structure in which a signal is input from the external terminal 401 is employed instead of the control circuit 121 used in the voltage regulator according to the second embodiment. Through the input of an “H” or “L” signal from the external terminal 401, manual selection may be achieved between a voltage regulato...
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